Method and apparatus for changing main sheaves and cables on lift bridges



March 8 1927.

E. A. PEARSQN METHOD AND APPARATUS FOR CHANGING MAIN SHEAVES AND CABLES0N LIFT BRIDGES Filed July 21, 1924 Patented Mar. 8, 1927.

UNITED STATES PATENT f ERIC A. PEARSON, OF PORTLAND, OREGON.

METHOD AND APPARATUS POE CHANGING MAIN SI-EEAVES AND CABLES QN LIFTBRIDGES.

Application filed July 21, 1924. Serial No. v'727,/!f1=0.

My invention hasoforits objectthe providing of an improved means andmethod for repairing and replacing the main sheaves and cables of aso-called vertical lift bridge, without interfering with the operationof the lift span or with the traffic over the bridge.

The problem of accomplishing said work is especially present in thedouble-deck type of the vertical lift bridge. In this type the lowerdeck is suspcndedfrom the main deck and adapted Itobe liftedindependently of the main'deck to accommodate the smaller crafts-of theriver trai'iic, and is always first raised before the span on which themain deck is located is raised; the two decks being raised as a unitthereafter.

The total weight of the lifting deck and lift span of abridge of thistype is approximately 1600 tons and the counter weights,

cables and sheaves will weigh approximately 990 tons each, of whichthere are two sets of two sheaves each located one set in each tower.The main sheaves over which sixteen two and a quarter inch cables areoperated arefourteen feet in diameter and weigh approximately 32 tonseach.

" The cost and investment concerned in bridges or. thistype pie-supposeheavy and continuous duty both as to water traflic and land'traffic,which cannotibe and must not i be interrupted.

A" further specific and principal object of 'myi nveiition is to providea means and a inetho'dby which .the'said repair and replacement may beaccomplished in a simple, andrrelatively economical manner, and withoutinterfering with the operation or use of thebri'dge.

-My invention as a solution, to this problem consists in placing atemporary sheave element adjacentthe main sheave element to be repaired,and mounting a-movable girder at'each end of the lift spanbelow a fixedgirderthereof, and connecting said counterweights with said movablegirders by a temporary auxiliary cable element and then moving saidmovable girderfrom said fixed girder an interposed hydraulic power,thereby to suspend said counterweights by said temporary cable element.

' Heretofore, such similar problems, to the best of my knoivledgqhavebeen solvedby of absolute necessity.

constructing false work to support the lift span and the counter-weightswhiclrnecjessitated putting the lift span out of operation and closingthe bridge to both river and land trafiic for an indefinite time and thecost of which is prohibitiveexce 'j t in times Such method ofaccomplishing the replacement of the main sheaves 'ofa lift bridge isnot to be considered'where contracts and industrial conditions do notpermit that the continuous operation of the bridge 3 be interrupted aswell as the "rulings of the .Nar Department,which 'areto the effect thatnavigable streams musfibe left open for water traffic at all'times.

invention and Fig. 2 shows a front elevatlon of thesame tower andillustrates the 'relative arrangement of the temp and thelift span;

The usual type of liftbridge comprises approach spansQone or morei'iiinumbefl'fon orary sheaves and cables each side thelift span. The ends ofth e approach spans rest on suitable "piers"wliich also support thelifting towers on which the counter-weights and lifting [deck' and "liftspan are supported. l

As the method of replacing the main sheaves on either tower and (the11ear1s'employed will be exactly the same, I will only describe theoperation on onelt ower.

towersfrising from'piersfsuch as indicated at 1 upon each side of thewaterway includes vertical main columns 5,"sp'aced 'inclinedcolumns .6with struts andj'braces 7 and 8 to form a rigid structure. $a ifdftbwersare each providednear its top"with a' 'main girder 10 on which the mainsheaves 11 are supported in journalf-b ealring's 12. Ma n cables 13 areoperatively' mounted on sald ma n. sheaves and areconn'e'cted atone endwith, thegirder'15-on the lift'spa'n and at their other ends with acounterweight 16.

Sixteen main cables 13 are operatively mounted over each of the two mainsheaves 11 and are connected to the lifting girder 15 on the lift spanand to the counterweight 16.

The main sheaves of a vertical lift bridge are subjected to heavy duty,and are located as before mentioned at the top of a tower 173 feet ormore above low water, which height is generally required to provideclearance for all classes of vessels. The main sheaves of which thereare two on each tower, are arranged parallel but spaced apart.

To more clearly bring out the difiiculties to be surmounted in replacingthese sheaves, it should be understood that each sheave weighsapproximately 32 tons and is fourteen feet in diameter. The weight ofthe lifting deck and span weighs approximately 1600 tons and eachcounter-weight weighs approximately 800 tons, in order to counterbalance one-half the weight of the lift deck and span. With the weightof the thirtytwo two and one-quarter inch cables, sixteen of which areoperated over each sheave, brings a total weight over the two sheaves toapproximately 1700 tons, and the weight supported by one sheave is 850tons.

The problems consist in raising the total weight of 1700 tons off themain sheaves, and replacing each sheave which weighs 32 tons and isfourteen feet in diameter, and is located one hundred and seventy-threefeet or more in the air, without in any way interfering with theoperation of the bridge.

In making repairs or replacements of said main sheaves the liftingfunctions of the bridge have heretofore been rendered inoperative andthen thebridge becomes a source of great obstruction to trailic upon thewaterway' T o avoid this obstruction and to enable a full use of thewaterway during such repairs to the bridge I have devised an apparatusand a method whereby the lift span may be operated during the removaland replacement of the main sheaves or other extensive repairs to thecables or operative parts.

I first reinforce the main girder 10 upon which the sheaves 11 aresupported to provide for the additional weight which it must temporarilysupport, and then arrange two temporary sheaves 18 adjacent each mainsheave and arranged in pairs in alinement with each other and so thattheir outer peripheries are in vertical alinement with the outer edgesof the main sheaves.

Plates 23 are provided on each side of the counter-weight 16 and a plate22 is provided underneath the bottom of the counterweight and connectedto the side plates, thus forming a frame or sling for the counterweight.

Temporary cables are then fixed to the upper ends of the plates 23 andpassed over the temporary sheaves 18 and down to the lift span andconnected to a temporary girder 25 which is slidably mounted between.the span cords adjacent to and below the lifting girder 15 to which themain cables are fastened.

Hydraulic jacks are then placed between the fixed lifting girder 16 andthe slidable temporary girder 25, and are actuated to force the girder15 apart from the girder 25 until the temporary cables 20 become tautand take the weight of the lift deck and span and counter-weight fromoff the main cables 13, and the main sheaves 11, thus leaving the cablesslack. Blocks are then placed between the two girders 15 and 25 to holdthem spaced apart.

At any time during the operation as when the weight of the lift span isbeing shifted from the main sheaves to the temporary sheaves, and eitherset of cables are slack, the lift span may be operated on whichevercables are taut, or in case this is not practicable, the hydraulic jacksneed only be operated for not more than two minutes to bring the tautcables into the desired relation with the slack cables.

The main cables 13 may then be taken off the main sheaves 11, and thesheaves may be replaced or repaired as the case may be, by any suitablemeans with which those skilled in the art will be acquainted without inany way interfering with the operation of the bridge and with a verysubstantial saving in operating costs, time, and material.

After the repairs to the bridge are completed, such as the removal andreplacement of the main sheaves, the jacks 27 are again actuated toadmit of the fillers 28 being removed and the girder 25 is permitted toreapproach the girder 15 until the weight is again carried upon the maincables l i whereupon the temporary cables 20 may be removed as well asthe frame from about the counterweight. I

Having described my invention, what I claim is:

1. In a lift bridge, in combination with the main sheaves, and cablessupported on said sheaves having their opposite ends secured to the liftspan of the bridge and a counterweight, respectively, of pairs ofsmaller sheaves wherefrom temporary cables are disposed in verticalalignment with said main cables, said temporary cables being connectedat their opposite ends with said counterweightand lift span, a frameabout said counterweight through which connec tion between the temporarycables and the counterweight is made, a slidable girder mounted below atransverse girder in said lift span to which said temporary cables areconnected, and means to separate said slidable girder from saidtransverse girder to transfer the tension from said main cable to saidtemporary cables.

2. The method of changing the main cables sheaves of a lift bridge,consisting in placing a pair of temporary sheaves of smaller diameteradjacent the main sheaves to be replaced, mounting a girder at each endof the lift span in slidable relation below a transverse fixed girderthereof, securing a plurality of temporary cables to said slidablegirder and to the counterweight running over said pairs of sheaves,respectively, and separating said slidable and said fixed girders torelieve the tension on the main cables whereupon the main cables may beremoved.

3. In a riggers device: the combination of a pair of relatively smallsheaves adapted to replace temporarily a single larger sheave; a movablegirder positioned adjacent a permanent girder of the structure beingoperated upon; means for separating said girders; flexible memberssecured to said movable girder and passing over said small sheaves; andmeans for securing said flexible members to a counterweight.

4. In a riggers repair device: flexible hoisting members; temporarilypositioned sheaves for said flexible members adjacent a permanentsheave; a cage adapted to receive a counterweight secured to saidflexible members; a movable girder mounted upon the structure to besupported by the device; and means for placing the load upon saidflexible members by moving said girder.

5. In a lift bridge of the character described, the method of repairingthe suspending means of the counter-Weights consisting in placing atemporary sheave element adjacent the main sheave element to berepaired, mounting a movable girder at an end of the'lift span below afixed girder thereof, connecting said counterweights with said movablegirders by a temporary auxiliary cable element, and then moving saidmovable girder from said fixed girder by an interposed mechanical power,thereby to suspend said counterweights by said temporary cable element.

6. In a lift bridge of the character described, the method of repairingthe suspending means of the counter-weights co11- sisting in placing atemporary sheave element adjacent the main sheave element to berepaired, mounting a movable girder at an end of the lift span below afixed girder thereof, connecting said counter-weights with said movablegirders by a temporary auxiliary cable element, and then moving saidmovable girder from said fixed girder by an interposed hydraulic power,thereby to suspend said counter-weights by said temporary cable element.

ERIC A. PEARSON.

